The mystery of whether Ernest Hemingway’s widow volunteered or was coerced into leaving their Cuban house to the nation has come a step closer to being solved, with the discovery of a letter in which she states that her late husband “would be pleased” that Finca Vigía be “given to the people of Cuba … as a centre for opportunities for wider education and research”.

Hemingway lived on the 19th-century Cuban farm for 21 years, between 1939 and 1961, writing his masterpieces The Old Man and the Sea and For Whom the Bell Tolls there as well as posthumously published works including A Moveable Feast and Islands in the Stream. He committed suicide in Idaho in 1961. The property became a museum in 1962, but it has been unclear whether this was following the wishes of Mary Hemingway, his fourth wife, or at the insistence of the Cuban government, with differing accounts from different parties.

The newly discovered letter, dated 25 August 1961, sees Mary Hemingway specifically donate the Finca Vigía to the Cuban people. “…Whereas – my husband, Ernest Hemingway, was for twenty-five years a friend of the Pueblo of Cuba … he never took part in the politics of Cuba … he never sold any possessions of his, except his words, having given away cars, guns, books and his Nobel prize medal to the Virgen del Cobre,” she wrote to her husband’s friend Roberto Herrera.

“I believe that he would be pleased that his property … in Cuba be given to the people of Cuba … as a center for opportunities for wider education and research, to be maintained in his memory. With this document, as the only heir of Ernest’s estate, I hereby give to the people of Cuba this property, in the hope that they will learn and profit from, and enjoy it, as much as Ernest and I did.”

Sold this week via Alexander Historical Auctions, the letter was found among the papers of Herrera. “Ernest Hemingway had committed suicide in Ketchum less than two months earlier. However, at some point shortly thereafter, Mary backtracked and stated that after Hemingway’s suicide, the Cuban government contacted her in Idaho and announced that it intended to expropriate the house, along with all real property in Cuba. These documents show that Mary did indeed intend to donate the home to the Cuban people,” said the auction house in its catalogue. The handwritten note was snapped up on Wednesday for $1,100 (£716), a price well below the estimate of $2,000-$3,000.

Valerie Hemingway – who was Ernest’s secretary before marrying his youngest son, whom she met at the author’s funeral – went to Finca Vigía with Mary shortly after Hemingway’s death to sort through his papers. She said via email that “what is being auctioned is a draft of a memo Mary intended to give to [Fidel] Castro that Roberto Herrera was going to translate. As far as I can remember Mary never actually sent the memo; she gave the draft to Roberto afterwards.”

Her own memoir, Running with the Bulls: My Years with the Hemingways, sees Valerie write that Mary “genuinely wanted to see her husband’s memory endure by creating a shrine of the home he loved and dedicating it to the Cuban people, among whom he had lived for more than a third of his life … Mary’s first idea was that the finca would become a learning centre, and to that end she wanted to leave there as complete a record of her husband’s life and most especially of his work as was prudent.”

But Naomi Wood, author of the novel Mrs Hemingway, said that Mary Hemingway’s own memoir suggests the situation was not quite as straightforward. “The question is whether the Hemingway house was ‘donated’ by Mary, or coerced from her, or extracted from her via diplomacy. In all likelihood it was a mixture of all three,” she said.

Hadley Freeman: Me and Mrs Hemingway

“In her memoir, How It Was, she uses the words ‘acquisition’ and ‘appropriation’, which suggests the takeover of Hemingway’s property was done with some unwillingness on her part, rather than a donation as the auctioned letter suggests. Though the auctioned letter suggests a donation, her memoir suggests bullying, though Castro does it in the most gentlemanly fashion, even asking her: ‘Why don’t you stay here with us in Cuba?’”

Mary Hemingway recounts a telephone conversation from the time in How it Was, in which she says to a Cuban official that “I’m not sure if I wish to give you our finca. [They could appropriate it, of course, as they had done to so much US property there.] Perhaps your government would give me permission to go down to remove our personal papers. Would you find out and call me back tomorrow? This same hour? Muy bien.”

She was advised, she writes, “to take the chance of recovering Ernest’s manuscripts, if nothing more. By this time United States citizens were prohibited journeys to Cuba, but the US immigration authorities in Miami gave me the exit and re-entry permits.”

The author’s widow would bring back crates of papers on a shrimp boat travelling from Havana to Tampa. “Mary also recounts her negotiations with Castro to remove a few paintings back to the US: including a Paul Klee and Juan Gris,” said Wood. “She also manages to remove Hemingway’s wax-sealed manuscripts they’d found at the Banco Nacional. Mary’s cargo left on a shrimp boat back to Tampa, which was the last to have any clearance papers from the US. More importantly for scholars than the nature of the deal for the Finca Vigía donation or appropriation was the fact that she managed to get those manuscripts out.”

Dr Susan Beegel, editor emerita of The Hemingway Review, said the discovery of the letter – first covered in Fine Books & Collections – was “new and interesting”.

“It’s nice to see her thoughts on how she intended the people of Cuba to enjoy the museum – still thriving today,” said Beegal. “It’s well-known that Mary deeded the Finca Vigía to the people of Cuba. After the Castro revolution, the house could have been appropriated, as was the case with other US property in Cuba, but instead the Cuban government approached Mary to request the house as a gift, to be used as a monument to Hemingway. She negotiated with them (and the Kennedy administration as well, because US citizens were not allowed to visit Cuba) to be able to return and remove personal belongings, art, and Hemingway’s manuscripts from the house in exchange for the donation.”

This article was amended on 14 February 2015. The name of the Hemingways’ boat is Pilar, not Filar. This has been corrected.